1. Field of the Invention
The present invention relates generally to an ink-jet printing apparatus. More specifically, the invention relates to an ink-jet textile printing apparatus for performing printing on a cloth or so forth.
2. Description of the Related Art
As typical method for performing printing on a cloth, a wall paper and so forth, a screen textile printing method for performing direct printing on the cloth and so forth employs a silk screen printing plate. In this method, with respect to an original image, at first, the silk screen printing plates are prepared for respective colors used in the original image. Then, the silk screen printing plate is loaded on a screen textile printing apparatus to perform printing by directly transferring an ink to the cloth or so forth through a mesh of the silk screen printing plate.
However, in such screen textile printing method, a huge amount of process steps and working days are required for preliminarily preparing the silk screen printing plates. Further operation is required for blending of inks for respective colors, and registering of the silk screen printing plate per each color. In addition, the screen textile printing apparatus per se is bulky, and the size of the apparatus is increased in proportion to number of colors to be used to require a substantial space for installation. Also, a space for storing the silk screen printing plates become necessary.
Therefore, it has been proposed an ink-jet textile printing system for performing printing directly on a printing medium, such as the cloth, the wall paper and so forth. The ink-jet textile printing system is to eject a fine ink droplet through ejection openings of an ink-jet head to perform printing an image or so forth by forming ink dots on the printing medium. The ink-jet textile printing system has many advantages such that there is not required the screen printing plate which has been required in a conventional screen textile printing system, and process steps and working days for forming the image on the cloth significantly shorten. Furthermore, the ink-jet textile printing system is advantageous for capability of down-sizing of the apparatus. In addition, since printing information for printing can be stored in various storage media, such as tape, flexible disk, optical disk and so forth, the ink-jet textile printing system is superior in safekeeping and storage of the printing information. Furthermore, the ink-jet textile printing system is advantageous in easiness of processing of the printing information, such as changing of color, layout, expansion and contraction of the image and so forth.
On the other hand, cloths as printing medium to be employed in the ink-jet textile printing system, extend in wide variety, such as natural fibers, e.g. cotton, silk, wool and so forth, synthetic fibers, e.g. nylon, rayon, polyester and so forth, and mixed fabric of these fibers. Accordingly, in order to satisfactorily perform printing for the cloth consisted of such wide variety of fibers, it is desirable to adapt dye of the ink to a material of respective fibers. For example, reactive dye is preferred for cotton and silk, acid dye is preferred for nylon, disperse dye is preferred for polyester fiber, metal complex salt dye is preferred for wool, and vat dye or pigment is preferred for cotton. Amongst, disperse dye, metal complex dye, vat dye and pigment are known as a coloring agent insoluble in water or a coloring agent having low solubility in water.
Associating with necessity of use of inks depending upon kinds of the printing medium, following several problems occur.
First of all, in order to prepare water based ink employing water insoluble dye or dye having low solubility, it is typically performed to prepare fine particle of material of dye and to disperse the fine particle dye material into water by dispersing agent for emulsification. However, when the water based ink in which the dispersing agent is dispersed and emulsified, coagulation and sedimentation of the dye in the ink can be caused as the time going to cause variation of dye density resulting in fluctuation of printing density, or, in turn to cause plugging of an ink passage.
With respect to such problem, there has been proposed in Japanese Patent Application Laid-open No. 57342/1986 to provide a function for stirring the ink to prevent the coagulation or the sedimentation of the dye in the ink by constantly operating such stirring function.
However, only by the construction of the prior art proposed in the above-identified publication, it can be insufficient for satisfactorily using the water based ink employing the water insoluble or the dye having low solubility.
For example, in the case that a motor for performing stirring is driven constantly during use of the ink-jet textile printing apparatus, it is inherent that a bubble is generated in the ink and dissolved oxygen is absorbed into the ink. Even when stirring force is made smaller, it is still difficult to completely avoid generation of the bubble. In such case, according to elevating of an ink temperature, the bubble and the dissolved oxygen may be grown to form a greater bubble. Such large bubble may be a cause of faulty ejection, such as ink ejection failure and so forth. The problem of the faulty ejection caused by the grown bubble is particularly remarkable in the case where a head of the system for ejecting the ink by generating bubble utilizes thermal energy.
On the other hand, in the case that a period of stirring is excessively long, it is experimentally confirmed that dispersing ability of the dye can be lowered to cause fluctuation of the printing density. A reason for causing the fluctuation is estimated as follows. By stirring, a possibility of collision between dye molecules can be increased to accelerate coagulation, and the sedimentation of the dye can be promoted to cause non-uniformity of the ink density. Also, by acceleration of the coagulation, an average grain size of the dye becomes greater to cause plugging in a filter in the ink passage or plugging in the ejection openings.
Furthermore, a construction of the prior art is not practical even in the viewpoint of a life of a stirring motor. More specifically, in the case of a textile printing apparatus, different from an ordinary printer used in an office, it is typical to be operated continuously over whole days, i.e. 24 hours, and requires a durability of the apparatus over 5 years or more, as industrial facility. Accordingly, a required lift for the stirring motor should be quite long in operation period. It is quite difficult to find out the motor satisfying such requirement. On the other hand, as one solution for solving such problem, the motor may be replaceable. However, this is not desirable in view of construction of the overall apparatus and in the viewpoint of cost.
Secondly, among various dyes, properties are differentiated such that the reactive dyes, acid dye are water soluble, whereas dispersing dye, metal complex salt dye, vat dye and pigment are water insoluble or have low solubility. Accordingly, physical property, characteristics and so forth of the inks are differentiated.
However, in the conventional ink-jet textile printing apparatus, when the inks having different properties are used, dedicated apparatus adapted for respective inks are employed and set to a use condition adapted to respectively corresponding inks. Therefore, cost for printing is increased. Also, a large space is required for installing a plurality of textile printing apparatuses.